KR101855083B1 - Magnet for physical vapor deposition processes to produce thin films having low resistivity and non-uniformity - Google Patents

Abstract

Apparatus and methods for depositing thin films with high thickness uniformity and low resistivity are provided herein. In some embodiments, the magnetron assembly includes a shunt plate rotatable about an axis, an inner closed loop stimulus coupled to the shunt plate, and an outer closed loop stimulus coupled to the shunt plate, wherein the inner closed loop stimulus The imbalance rate of the magnetic field strength of the outer closed loop stimulus to the magnetic field strength is less than about one. In some embodiments, the imbalance rate is about 0.57. In some embodiments, the shunt plate and the outer closed loop stimulus have a heart shape. A method of using RF and DC power in combination with the magnetron assembly of the present invention is also disclosed.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a magnet for physical vapor deposition processes for producing thin films having low resistivity and nonuniformity,

Embodiments of the present invention generally relate to substrate processing, and more particularly to physical vapor deposition processes.

For example, in conventional physical vapor deposition (PVD) processes for tungsten (W) deposition, only direct current (DC) power was applied for film deposition. Although conventional magnetron designs can achieve good thickness uniformity, the resulting resistivity of the deposited W films is very high, which limits transistor integration density due to high line resistance. One technique that attempts to improve the properties of W films is radio frequency (RF) assisted PVD deposition where the resistivity of the W film can be significantly reduced due to high energy ion re-sputtering and film densification . However, due to the RF power coupling of the plasma during the deposition process, the thickness uniformity of these W films is poor.

Thus, the present inventors have provided apparatus and methods for PVD deposition of thin films with reduced resistivity and non-uniformity.

Apparatus and methods for depositing thin films with high thickness uniformity and low resistivity are provided herein. In some embodiments, the magnetron assembly includes a shunt plate rotatable about an axis, an inner closed-loop magnetic pole coupled to the shunt plate, and an outer closed-loop stimulus coupled to the shunt plate. And the unbalance ratio of the magnetic field strength of the outer closed loop stimulus to the magnetic field intensity of the inner closed loop stimulus is less than about one. In some embodiments, the ratio is about 0.57. In some embodiments, the outer closed loop stimulus has a cardioid shape.

In some embodiments, a method of processing a substrate in a physical vapor deposition (PVD) chamber includes providing a process gas having at least some ion species into the PVD chamber, directing ion species toward the target, Applying a DC power to the target disposed on the substrate, rotating the magnetron on the target, the magnetron having an inner closed loop stimulus and an outer closed loop stimulus, the outer closed loop for the magnetic field strength of the inner closed loop stimulus, The imbalance rate of the magnetic field strength of the stimulus is less than about 1, sputtering metal atoms from the target using ion species, depositing a first plurality of metal atoms on the substrate, depositing a metal deposited using ion species Applying RF power to an electrode disposed below the substrate for reputtering at least a portion of the atoms, Applying a DC power and RF power during the period between to and forming a layer on a substrate. In some embodiments, the layer comprises tungsten (W), has a thickness uniformity of less than about 2% and a resistivity of less than about 10 [micro] [Omega] -cm.

Hereinafter, other and further embodiments of the present invention will be described.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention, which are briefly summarized above and discussed in greater detail below, may be understood with reference to the illustrative embodiments of the invention shown in the accompanying drawings. It should be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments to be.
Figure 1 illustrates a bottom perspective view of a magnetron in accordance with some embodiments of the present invention.
Figure 1A shows a partial bottom view of a magnetron in accordance with some embodiments of the present invention.
Figure 2 illustrates a side schematic view of a physical vapor deposition chamber in accordance with some embodiments of the present invention.
Figure 3 shows a graph of the deposited layer thickness along the wafer surface as a function of the unbalance rate of the outer pole to the inner pole of the magnetron using only DC power in accordance with some embodiments of the present invention.
Figure 4 shows a graph of deposited layer thickness along a wafer surface as a function of the unbalance rate of the outer pole to the inner pole of the magnetron using both RF and DC power in accordance with some embodiments of the present invention.
Figure 5 shows a graph of thickness uniformity and resistivity of a deposited layer as a function of the unbalance rate of the outer pole with respect to the inner pole of the magnetron in accordance with some embodiments of the present invention.
To facilitate understanding, the same elements that are common to the figures have been represented using the same reference numerals whenever possible. The drawings are not drawn to scale and can be simplified for clarity. It is contemplated that the elements and features of one embodiment may be advantageously incorporated in other embodiments without further recitation.

Apparatus and methods for depositing thin films with high thickness uniformity and low resistivity are provided herein. Some embodiments of the apparatus of the present invention are directed to magnetron designs for use in radio frequency (RF) physical vapor deposition (PVD) processes. Some embodiments of the method are directed to depositing thin films having high thickness uniformity (e.g., less than about 2%) and low resistivity (e.g., less than about 10 μΩ-cm).

Figure 1 illustrates a magnetron in accordance with some embodiments of the present invention. The magnetrons of the present invention generally include an RF power applied to one or more of a target or substrate support of a PVD chamber, such as, for example, the PVD chamber 200 shown in FIG. 2 and described below, Power PVD chambers. Non-limiting examples of processes that may benefit from using the magnetron of the present invention include tungsten (W) deposition processes among other deposition processes.

Figure 1 illustrates a bottom perspective view of a magnetron 100 in accordance with some embodiments of the present invention. The magnetron 100 includes a shunt plate 102 that also serves as a structural base for the magnetron assembly. The shunt plate 102 may include a rotating shaft 104 and the shunt plate 102 may rotate about its rotational axis when coupled to the shaft. For example, a mounting plate (not shown) for mounting the shunt plate 102 on a shaft (e.g., the shaft 216 shown in FIG. 2) is mounted on the shunt plate 102 to provide rotation of the magnetron 100 during use. Lt; / RTI > In some embodiments, and as shown, the shunt plate 102 may have a heart shape. However, the shunt plate 102 may also have other shapes.

The magnetron 100 includes at least two magnetic poles, e.g., an inner pole 106 and an outer pole 108. Each of the inner pole 106 and the outer pole 108 may form a closed loop magnetic field. As used herein, a closed loop magnetic field refers to a pole that has no separate beginning and end but instead forms a loop. The polarities between the respective poles 106 and 108 are opposite (e.g., the inner north pole and the outer south pole, or the inner south pole and the outer north pole), although the polarities within a given pole are the same (e.g.

Each pole may comprise a plurality of magnets arranged between the pole plate and the shunt plate 102. For example, the inner pole 106 includes a pole plate 110 having a first plurality of magnets 112 disposed between the pole plate 110 and the shunt plate 102. The outer pole 108 includes a pole plate 114 having a second plurality of magnets 116 disposed between the pole plate 114 and the shunt plate 102. The pole plates 110 and 114 may be made of a ferromagnetic material, such as, but not limited to, 400 series stainless steel or other suitable materials. The pole plates (110, 114) may have any suitable closed loop shape. The shapes of the pole plates 110 and 114 may be similar so that the distance between the pole plates 110 and 114 is substantially uniform around the loops of the pole plates 110 and 114. As shown, in some embodiments, pole plate 114 may be in the form of a heart. In some embodiments, the pole plate 114 can follow the peripheral edge of the shunt plate 102 roughly.

The magnets in each of the plurality of magnets need not be distributed completely uniformly. For example, as shown in FIG. 1, in some embodiments, at least some of the magnets in the second plurality of magnets 116 may be arranged in pairs. As shown in FIG. 1A, a plurality of magnets may be arranged in a plurality of rows. For example, a first plurality of magnets 112 are shown arranged as magnets of two rows of magnets.

Referring back to FIG. 1, in some embodiments, the magnetic strength of each magnet in the first and second plurality of magnets 112, 116 may be the same. Alternatively, the magnetic strength of one or more magnets in the first and second plurality of magnets 112, 116 may be different. In some embodiments, the intensity of the magnetic field formed by the inner pole 106 may be stronger than the intensity of the magnetic field formed by the outer pole 108. Thus, in some embodiments, the magnets of the first plurality of magnets 112 may be packed more densely than the magnets of the second plurality of magnets 116. Alternatively, or in combination, in some embodiments, the number of magnets in the first plurality of magnets 112 may exceed the number of magnets in the second plurality of magnets 116.

The disparity in the strength of the magnetic fields between the inner and outer poles 106 and 108 can be defined by the unbalance rate of the magnetic poles of the inner poles 106 relative to the magnetic poles of the outer poles 108. For example, in embodiments in which each of the magnets in the first and second plurality of magnets 112, 116 are equivalent magnets with equivalent magnetic field strength, the unbalance rate is greater than the magnitude of the magnets in the first plurality of magnets 112, The ratio of the number of magnets in the second plurality of magnets 116 to the number of magnets in the second plurality. In the magnetron of the present invention disclosed herein, the present inventors have found that those having an imbalance rate of less than about 1, for example, the magnetic field strength at the outer pole 108, which is smaller than the magnetic field strength of the inner pole 106, and / Having a number of magnets in a second plurality of magnets 116 that is less than the number of magnets in the first plurality of magnets 112 is advantageous because of the high thickness uniformity and low resistivity ≪ / RTI > For example, in some embodiments, the preferred imbalance rate may be about 0.57. It is contemplated that other imbalance rates may be used for specific applications. For example, as described below in connection with FIGS. 3-4, the inventors have discovered that an imbalance rate can be selected or changed to control the thickness profile of a deposited film.

Figure 2 illustrates a side schematic view of a process chamber 200 in accordance with some embodiments of the present invention. The process chamber 200 may be any suitable PVD chamber configured for DC and optionally RF power. In some embodiments, the process chamber 200 may be configured to apply both DC and RF power, as described below. For example, the process chamber 200 includes a substrate support 202 over which the substrate 204 is disposed. Electrode 206 may be disposed on substrate support 204 to provide RF power to process chamber 200. RF power can be supplied to the electrodes via the RF power supply 208. [ RF power supply 208 may be coupled to electrode 206 via a match network (not shown). Alternatively, or in combination, an RF power supply 208 (not shown) (or other RF power supply) may be coupled to a target 210 disposed on a ceiling of the process chamber 200, ) (Or to an electrode disposed proximate the backside of the target).

The target 210 may comprise any suitable metal and / or metal alloy for use in depositing layers on the substrate 204. For example, in some embodiments, the target may comprise tungsten (W). A DC power supply 212 may be coupled to the target 210 to provide a bias voltage on the target 210 to direct the plasma formed in the chamber 200 toward the target 210. The plasma may be formed from a process gas such as argon (Ar) or the like that is provided to the chamber 200 by a gas source 213. A magnetron assembly 214 including a magnetron 100 and a shaft 216 for rotating the magnetron 100 is disposed on the target 210. The magnetron assembly 214 may be formed, for example, by a uniform deposition of a layer of metal atoms on the substrate 204 with high thickness uniformity and low resistivity as described above, and / or uniform deposition of metal atoms from the target 210 Sputtering can be facilitated.

A controller 218 may be coupled and provided to various components of the process chamber 200 to control the operation of various components of the process chamber 200. The controller 218 includes a central processing unit (CPU), memory, and support circuits. The controller 218 may control the process chamber 200 through computers (or controllers) associated with a particular process chamber and / or support system components, or directly. The controller 218 may be any one of any type of general purpose computer processor that may be used in an industrial environment to control various chambers and sub-processors. The memory or computer readable medium of controller 218 may be embodied in a computer readable medium such as a random access memory (RAM), read only memory (ROM), floppy disk, hard disk, optical storage medium (e.g., a compact disk or digital video disk) Or any other form of readily available memory, such as local or remote digital storage. Supporting circuits are coupled to the CPU to support the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input / output circuits and subsystems, and the like. The inventive methods described herein may be stored in memory as a software routine that may be executed or invoked to control the operation of the process chamber 200 in the manner described herein. The software routines may also be stored and / or executed by a second CPU (not shown) located remotely from the hardware being controlled by the CPU.

In operation, a gas such as argon (Ar) is provided from the gas source 213 to the process chamber 200. The gas can be provided at a sufficient pressure such that at least a portion of the gas comprises ionized species such as Ar ions. The ionized species are directed to the target 210 by a DC voltage applied to the target 210 by the DC power supply 212. The ionized species collide with the target 210 to release metal atoms from the target 210. Metal atoms having a neutral charge, for example, are dropped toward the substrate 204 and deposited on the substrate surface. Simultaneously with the collision of the ion species with the target 210 and the subsequent release of the metal atoms, the magnetron 100 is rotated on the target 210 about the shaft 216. The magnetron 100 is generally parallel to the surface of the target 210 to capture electrons capable of colliding with any gas molecules near the target 210 and capable of ionizing any of the gas molecules, In the chamber 200, which in turn increases the density of local ion species near the surface of the target 210 and increases the sputtering rate. RF power may also be applied to the substrate support 202 by the RF power supply 208 during sputtering of metal atoms from the target 210. The RF power can be used to direct some of the ionized species toward the deposited metal atoms on the substrate 204 to promote at least some of the metal atoms deposited from the layer being formed on the substrate 204 . Re-sputtering of the deposited metal atoms can reduce the resistivity in the deposited layer and can promote densification of the layer. However, as described below, the inventors have found that RF power alone can result in a layer having a suitable resistivity, but having a center high-edge low profile. Thus, the magnetron 100 of the present invention having a desired imbalance rate as described above can be used alone or in combination with RF power, for example, to provide a preferred deposition profile with high thickness uniformity and low resistivity.

Figure 3 shows a graph of the deposited layer thickness along the wafer surface as a function of the unbalanced rate of the outer pole to the inner pole of the magnetron using only DC power in accordance with some embodiments of the present invention. For example, if the imbalance rate is substantially greater than about 1, such as about 2.7, the deposition profile has a high center and a low edge profile, as shown by plot 302. To increase metal ionization by controlling ion bombardment on the substrate and / or by shrinking confinement volumes, a magnetron with an imbalance rate greater than about 1 may be used. For example, to modulate the deposition profile, an imbalance rate of less than about one may be used. For example, as shown in FIG. 3, a deposition profile with an imbalance rate of less than 1 may be compared to a plot 304 (e.g., having an imbalance rate of about 0.97) and a plot 306 (e.g., having an imbalance rate of about 0.57) ), As shown in Fig. In some embodiments, the lower the unbalance rate, the lower the central deposition (as shown by the plot 304 and plot 306) and the higher the edge deposition. However, adding RF power (RF power alone will result in a high center and low edge profile, as described above), and a preferred deposition profile can be achieved as shown in FIG. 4 below.

Figure 4 shows a graph of deposited layer thickness along a wafer surface as a function of the unbalanced rate of the outer pole to the inner pole of the magnetron using both RF and DC power in accordance with some embodiments of the present invention. For example, to deposit a layer with high thickness uniformity and low resistivity, as described above, a combination of RF and DC power using an unbalance rate of less than one may be used. Because RF power is coupled at the wafer center via ESC, the film deposition due to RF power has a thick center and a thin edge profile. Due to the low unbalance rate of the magnetron 100 of the present invention, a deposition profile in which the wafer edge is thick and the wafer center is thin, due to plasma diffusion and weak magnetic field bounding to the wafer edge, can be realized with DC power PVD deposition have. By depositing RF power and DC power in combination, a uniform thickness profile can be achieved across the substrate. For example, using DC and RF power to deposit a thin film, as shown in FIG. 4, a large unbalance rate (e.g., in the range of about 1 to about 2.72) May result in the deposition of a layer with a high, low edge profile. However, in embodiments where the imbalance rate is low, for example in the range of about 0.57 (e.g., plot 402) to about 0.93 (e.g., plot 404), such a process may be more uniform May result in the deposition of a layer with one profile.

Also, as discussed above, RF power can improve the resistivity in the deposited layer, but unfortunately when it is provided alone, the profile of the deposited layer results in a high center and low edge. Thus, by combining RF power with DC power using the magnetron 100 of the present invention, a deposited layer with high thickness uniformity and low resistivity can be achieved. As shown in FIG. 5, due to the magnetron 100, the resistivity of the deposited layer may be much lower than the resistivity of the layer deposited using a conventional PVD process. 5 also shows that changing the imbalance rate in the magnetron 100, as indicated by the plot 504, has little or no substantial effect on the resistivity of the deposited layer. However, as shown in FIG. 5, reducing the imbalance rate can substantially improve the thickness uniformity of the deposited layer, as shown by the plot 502.

For example, in some embodiments, using the inventive methods and apparatus disclosed herein, the resistivity of a 500 Angstrom tungsten (W) film was about 9.4 [micro] [Omega] -cm and the thickness uniformity was about 1.5%. These results show a significant improvement from a tungsten (W) film deposited using a conventional magnetron of DC power, with a resistivity of about 11 [micro] [Omega] -cm or more and a thickness uniformity of 2.5%.

Accordingly, apparatus and methods for depositing thin films with high thickness uniformity and low resistivity are provided herein. Some embodiments of the apparatus of the present invention are directed to magnetron designs for use in radio frequency (RF) physical vapor deposition (PVD) processes. Some embodiments of the method are directed to using RF and DC power for depositing thin films with high thickness uniformity (e.g., less than about 2%) and low resistivity (e.g., less than about 10 μΩ-cm).

Having described the embodiments of the invention in detail, other and further embodiments of the invention may be devised without departing from the basic scope thereof.

Claims (15)

A method of processing a substrate in a physical vapor deposition (PVD) chamber,
Providing a process gas having at least some ion species into the PVD chamber;
Applying DC power to a target disposed on the substrate to direct the ion species toward the target;
Rotating the magnetron on the target, the magnetron having an inner closed loop stimulus and an outer closed loop stimulus, the imbalance rate of the field strength of the outer closed loop stimulus relative to the field strength of the inner closed loop stimulus is less than 1, ;
Sputtering metal atoms from the target using the ion species;
Depositing a first plurality of metal atoms on the substrate;
Applying RF power to re-sputter at least a portion of the metal atoms deposited using the ion species; And
Forming a layer on the substrate by applying the DC power and the RF power for a desired time period,
Wherein the layer has a thickness uniformity of less than 2% and the layer has a resistivity of less than 10 < RTI ID = 0.0 >
A method of processing a substrate in a physical vapor deposition (PVD) chamber. The method according to claim 1,
The step of applying the RF power comprises:
Applying the RF power to an electrode disposed below the substrate;
Applying the RF power to the target; or
And applying the RF power to an electrode disposed near the target.
A method of processing a substrate in a physical vapor deposition (PVD) chamber. The method according to claim 1,
Wherein the imbalance rate is 0.57 to 0.97,
A method of processing a substrate in a physical vapor deposition (PVD) chamber. 4. The method according to any one of claims 1 to 3,
Wherein the target and the layer comprise tungsten (W).
A method of processing a substrate in a physical vapor deposition (PVD) chamber. A method of forming a tungsten-containing layer on a substrate,
Providing a process gas to a process chamber, the process chamber having a substrate support disposed within the process chamber and a target comprising a tungsten-containing material disposed opposite the substrate support within the process chamber, A substrate is disposed on the substrate;
Forming a plasma from the process gas;
Directing ion species formed in the plasma toward the target by applying a DC voltage to the target;
Sputtering tungsten-containing metal atoms from the target;
Rotating the magnetron over the target while sputtering tungsten containing metal atoms from the target, the magnetron having an inner closed loop stimulus and an outer closed loop stimulus, the inner closed loop stimulus being disposed within the outer closed loop stimulus , The imbalance rate of the magnetic field strength of the outer closed loop magnetic poles to the magnetic field strength of the inner closed loop magnetic poles is less than 1;
Depositing sputtered metal atoms on top of the substrate to form a tungsten-containing layer, wherein the tungsten-containing layer has a thickness uniformity of less than 2% and a resistivity of less than 10 mu OMEGA-cm; And
An electrode disposed within the substrate support during deposition of sputtered metal atoms to direct a portion of the ionized species toward the substrate to re-sputter at least a portion of the metal atoms deposited on the substrate; And applying power;
A method for forming a tungsten-containing layer on top of a substrate. 6. The method of claim 5,
Wherein the imbalance rate is 0.57 to 0.97,
A method for forming a tungsten-containing layer on top of a substrate. delete delete delete delete delete delete delete delete delete

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